Polymethyl methacrylate polymerization

Fig. 6-7 The Tromsdorff effect (autoacceleration) for polymethyl methacrylate polymerization [15].

All the data shown in Fig. 11-31 fall on a definite curve regardless of extrusion rate. Again, the curve shapes match polymethyl methacrylate polymerization curves. And, again, this would seem to indicate that chemical reaction was the prevailing rate process. 

After brief discussion of the state-of-the-art of modern Py-GC/MS, some most recent applications for stixictural and compositional chai acterization of polymeric materials are described in detail. These include microstixictural studies on sequence distributions of copolymers, stereoregularity and end group chai acterization for various vinyl-type polymers such as polystyrene and polymethyl methacrylate by use of conventional analytical pyrolysis. 

In another study, uniform composite polymethyl-methacrylate/polystyrene (PMMA/PS) composite particles in the size range of 1-10 fim were prepared by the seeded emulsion polymerization of styrene [121]. The PMMA seed particles were initially prepared by the dispersion polymerization of MMA by using AIBN as the initiator. In this polymerization, poly(7V-vinyl pyrolli-done) and methyl tricaprylyl ammonium chloride were used as the stabilizer and the costabilizer, respectively, in the methanol medium. Seed particles were swollen with styrene monomer in a medium comprised of seed particles, styrene, water, poly(7V-vinyl pyrollidone), Polywet KX-3 and aeorosol MA emulsifiers, sodium bicarbonate, hydroquinone inhibitor, and azobis(2-methylbu-... 

Grafting reactions onto a polymer backbone with a polymeric initiator have recently been reported by Hazer [56-60]. Active polystyrene [56], active polymethyl methacrylate [57], or macroazoinitiator [58,59] was mixed with a biopolyester polyhydroxynonanaate [60] (PHN) or polybutadiene to be carried out by thermal grafting reactions. The grafting reactions of PHN with polymer radicals may proceed by H-abstraction from the tertier carbon atom in the same manner as free radical modification reactions of polypropylene or polyhy-droxybutyratevalerate [61,62]. 

Formation of block polymers is not limited to hydrocarbon monomers only. For example, living polystyrene initiates polymerization of methyl methacrylate and a block polymer of polystyrene and of polymethyl methacrylate results.34 However, methyl methacrylate represents a class of monomers which may be named a suicide monomer. Its polymerization can be initiated by carbanions or by an electron transfer process, the propagation reaction is rapid but eventually termination takes place. Presumably, the reactive carbanion interacts with the methyl group of the ester according to the following reaction... 

Platinum-cobalt alloy, enthalpy of formation, 144 Polarizability, of carbon, 75 of hydrogen molecule, 65, 75 and ionization potential data, 70 Polyamide, 181 Poly butadiene, 170, 181 Polydispersed systems, 183 Polyfunctional polymer, 178 Polymerization, of butadiene, 163 of solid acetaldehyde, 163 of vinyl monomers, 154 Polymers, star-shaped, 183 Polymethyl methacrylate, 180 Polystyrene, 172 Polystyril carbanions, 154 Potential barriers of internal rotation, 368, 374... 

When the methyl methacrylate molecule polymerizes, it is polymethyl methacrylate—Plexiglas. 

Kinetic studies of the polymerization of mono-functional polymethyl methacrylate led to the determination of the propagation constants, k , of the sodium, potassium, and cesium salts 29- 35 36) of polymethyl methacrylates anions. Surprisingly, they... 

The kinetics of these oligomerizations initiated by a-lithio-methylisobutyrate (monomeric living polymethyl methacrylate) was reported by Muller et al. 50). A modified flow-tube technique, that permits to follow the polymerization for times as short as 0.02 s, was employed in this study. The reaction was performed in THF at... 

Polymerization of t-butyl methacrylate initiated by lithium compounds in toluene yields 100% isotactic polymers 64,65), and significantly, of a nearly uniform molecular-weight, while the isotactic polymethyl methacrylate formed under these conditions has a bimodal distribution. Significantly, the propagation of the lithium pairs of the t-Bu ester carbanion, is faster in toluene than in THF. In hydrocarbon solvents the monomers seem to interact strongly with the Li+ cations in the transition state of the addition, while the conventional direct monomer interaction with carbanions, that requires partial dissociation of ion-pair in the transition state of propagation, governs the addition in ethereal solvents. 

Various polymeric materials were tested statically with both gaseous and liquefied mixtures of fluorine and oxygen containing from 50 to 100% of the former. The materials which burned or reacted violently were phenol-formaldehyde resins (Bakelite) polyacrylonitrile-butadiene (Buna N) polyamides (Nylon) polychloroprene (Neoprene) polyethylene polytriflu-oropropylmethylsiloxane (LS63) polyvinyl chloride-vinyl acetate (Tygan) polyvinylidene fluoride-hexafluoropropylene (Viton) polyurethane foam. Under dynamic conditions of flow and pressure, the more resistant materials which binned were chlorinated polyethylenes, polymethyl methacrylate (Perspex) polytetraflu-oroethylene (Teflon). 

Another differential reaction is copolymerization. An equi-molar mixture of styrene and methyl methacrylate gives copolymers of different composition depending on the initiator. The radical chains started by benzoyl peroxide are 51 % polystyrene, the cationic chains from stannic chloride or boron trifluoride etherate are 100% polystyrene, and the anionic chains from sodium or potassium are more than 99 % polymethyl methacrylate.444 The radicals attack either monomer indiscriminately, the carbanions prefer methyl methacrylate and the carbonium ions prefer styrene. As can be seen from the data of Table XIV, the reactivity of a radical varies considerably with its structure, and it is worth considering whether this variability would be enough to make a radical derived from sodium or potassium give 99 % polymethyl methacrylate.446 If so, the alkali metal intitiated polymerization would not need to be a carbanionic chain reaction. However, the polymer initiated by triphenylmethyl sodium is also about 99% polymethyl methacrylate, whereas tert-butyl peroxide and >-chlorobenzoyl peroxide give 49 to 51 % styrene in the initial polymer.445... 

B. M. Ginzburg, L. A. Shibaev, V. L. Ugolkov, Effect of fullerene C60 on thermal oxidative degradation of polymethyl methacrylate prepared by radical polymerization, Russian Journal of Applied Chemistry, vol. 74, pp. 1329-1337, 2001. 

The column set was calibrated with a series of polystyrene stan rds with weight average molecular weights (Mw) between 2X10 and 4.1X10°. The standards were supplied by Pressure Chemical Co., Pittsburgh, Pa. and ArRo Laboratories, Inc., Joliet, 111. Other systems used in this work included the NBS-706 polystyrene standard and an emulsion polymerized polymethyl methacrylate sample. 

Fig. 23. Polymerization of monomers in masticating polystyrene and polymethyl methacrylate. Curves 1-6 1 ml methacrylic acid, styrene, methyl methacrylate, ethyl acrylate, acrylonitrile, and vinyl acetate, respectively, in 3 g polystyrene. Curves 7-12 2 ml methacrylic acid, methyl methacrylate, acrylonitrile, ethyl acrylate, styrene, and vinyl acetate, respectively, in 3g polymethyl methacrylate. The limiting viscosity numbers for points along Curves 2 and 3...

Methyl methacrylate is only one of a family of monomers, including the various esters of acrylic, methacrylic, and ethacrylic acids, which are polymerized to produce the thermoplastic resins known as the acrylates. A wide variety of reactions and starting materials may be utilized for their production however, the principal commercial product is polymethyl methacrylate, sold by Du Pont and Rohm Haas under the trade names of Lucite and Plexiglas, respectively. These materials were introduced to the United States market in 1936 (44) and have received widespread acceptance due principally to their outstanding optical properties. Production in 1949 was reported as about 22,000,000 to 25,000,000 pounds and peak wartime capacity was above30,000,000 pounds. While this can account for only about 2% of the current production of propylene for chemical purposes, the acrylate resins are of considerable commercial importance as they are sold at a relatively high price and are the only materials available that will meet the requirements for certain military and civilian products. 

Polymerization. Since fluorinated products are SCCO2 -philic, CO2 can be used as a substitute for CFC solvents in the production of fluoropolymers.5-7,38,39 Selection of fluorosurfactants has enabled polymerization of SCCO2-phobic polymers such as polymethyl methacrylate. " "" ... 

Onogi,S., Masuda,T., Ibaragi,T. Rheological properties of polymethyl methacrylate and polyvinyl acetate in the molten state. Kolloid-Z. Z. Polymere 222, 110-124... 

In the case of poly-menthyl-methacrylate, an evaluation of the type and degree of stereoregularity of the unfractionated polymers, obtained by different polymerization processes, has been made by converting poly-menthyl-methacrylate into polymethyl-methacrylate and then determining the stereoregularity of the methyl derivative thus obtained by N. M. R. analysis (135). 

According to this scheme, polymethyl methacrylate prepared in the absence of p benzoquinone should contain one initiator fragment per polymer molecule the addition of p benzoquinone to the polymerizing system should make this number tend towards two and at the same time the amount of combined quinone should approach one molecule per polymer molecule. Experiments with labelled initiator and labelled retarder (39) confirmed these predictions in general although not in detail. 

In contrast the polymerization of vinyl acetate in the presence of polymethyl methacrylate gives after selective precipitation appreciable amounts of pure graft copolymer, independently of the nature of the initiator moreover the degree of grafting, evaluated by infrared spectrometry, is about equally important. Similar results were obtained in the system vinyl acetate-polyethyl a-chloroacryl ate. 

The polyisoprenyl radicals (R ) initiate graft polymerization, while the hydrogen atoms do not lead to free polymethyl methacrylate but react more easily with rubber to form grafting sites, instead of initiating free chains. Evidently, if radicals directly derived from the monomer behaved in the same way, then almost quantitative graft copolymerization would be expected in the case of rubber (12, 221). 

The mechanical degradation and production of macroradicals can also be performed by mastication of polymers brought into a rubbery state by admixture with monomer several monomer-polymer systems were examined (10, 11). This technique was for instance studied for the cold mastication of natural rubber or butadiene copolymers in the presence of a vinyl monomer (13, 31, 52). The polymerization of methyl methacrylate or styrene during the mastication of natural rubber has yielded copolymers which remain soluble up to complete polymerization vinyl acetate, which could not produce graft copolymers by the chain transfer technique, failed also in this mastication procedure. Block and graft copolymers were also prepared by cross-addition of the macroradicals generated by the cold milling and mastication of mixtures of various elastomers and polymers, such as natural rubber/polymethyl methacrylate (74), natural rubber/butadiene-styrene rubbers (76) and even phenol-formaldehyde resin/nitrile rubber (125). 

It was also described that some common vinyl polymers, such as polymethyl methacrylate prepared with benzoyl peroxide, are able to initiate a further polymerization if heated in the presence of a second monomer [158). These phenomena must be interpreted by the existence of peroxide links inside the polymethyl methacrylate chain [229). Indeed any activity is destroyed on prolonged heating and this polymer can be used for initiating the polymerization of styrene. However the relative length of the sequences and the molecular weight of the product before and after copolymerization have not yet been determined. 

Hirshfeeld, S. M., and L. C. Anderson Polymerization of methyl methacrylate induced by gamma irradiated polymethyl methacrylate. J. Polymer. Sci. 37, 542 (1959). 

The case of "living polystyrene and methyl methacrylate is somewhat similar. It was shown, as should be expected, that "living polymethyl methacrylate does not initiate styrene polymerization (70), i. e. methyl-methacrylate is a terminator for the latter polymerization, although its addition to living poly-styrene initiates its polymerization. Hence, one may produce a block polymer by adding methyl methacrylate to "living polystyrene but not vice-versa (9,10). 

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